This invention relates to an object lens supporting unit for supporting an object lens used in an optical pick-up of an optical disk drive, in particular, to the unit supporting so as to permit the object lens to move by suspension wires and a method of assembling the unit.
Generally, as a recording apparatus connected to an electrical apparatus such as a personal computer, a recording apparatus using a semiconductor memory chip or using magnetically and/or optically recording medium is well known. An optical disk drive as a kind of the lafter can read data from an optical recording medium of disk type by irradiating laser beam to the medium and optically sensing reflected laser beam from the medium. The object lens supporting unit according to this invention is applied to the optical disk drive. The optical disk drive can further write data to the optical recording medium of disk type by irradiating laser beam to the medium. The object lens supporting unit according to this invention is applied to the optical disk drive.
The optical recording media of disk type are roughly classified into media capable of reading only or media capable of reading and writing. As the media capable of reading only, an Audio CD (an Audio Compact Disc), a CD-ROM (a Compact Disc-Read Only Memory), a DVD-Audio (a Digital Versatile Disc-Audio), a DVD-Video (a Digital Versatile Disc-Video), a DVD-ROM (a Digital Versatile Disc-Read Only Memory), and an SACD (a Super Audio Compact Disc) have been known. As the media capable of reading and writing, a CD-R (a Compact Disc-Recordable), a CD-RW (a Compact Disc-ReWritable), a DVD-RAM (a Digital Versatile Disc-Random Access Memory), and a DVD-RW (a Digital Versatile Disc-ReWritable) have been known.
In order to write data to the CD-R, it is necessary to use an optical disk drive for the exclusive use and a writing application software for the exclusive use. In the CD-R, it is impossible to delete data written once thereon while it is possible to additionally and repeatedly write new data thereon.
A conventional object lens supporting unit applied in a CD-R drive as an optical disk drive will be described.
The CD-R drive has an optical pick-up. The optical pick-up is driven in a direction that traverses innumerable tracks formed on a CD-R and is stopped on a target track so as to irradiate a laser beam to the target track and to optically sense a reflected laser beam from the target track/irradiate a laser beam to the target track. The optical pick-up has a laser source for generating the laser beam, an optical system for transmitting the laser beam irradiated from the laser source to the CD-R and reflected by the CD-R, and a light sensor for sensing the reflected laser beam. The optical pick-up is movable in a tracking direction (a diameter direction of the CD-R). Furthermore, an object lens included in the optical system is supported by an object lens supporting unit so that it is slightly movable in the tracking direction and a focusing direction (a thickness direction of the CD-R).
The optical pick-up of the CD-R drive is designed so as to deal with both of reading data from the CD-R and writing data to the CD-R because the CD-R is capable of reading and writing data. Herein, a power of the laser beam of the optical pick-up must be changed at which data are read and data are written. This is because it is necessary for writing data a power higher than a power for reading data in order to form pits on the CD-R by irradiating the laser beam. For example, the power for writing is approximately 10 to 20 times as high as the power for reading.
The laser beam generated from the laser source is transmitted through the optical system (a diffraction grating, a beam splitter, a collimator, and the object lens) and irradiated on the CD-R. On the other hand, the laser beam reflected from the CD-R is transmitted through the optical system (the object lens, the collimator, and the beam splitter) and sensed by the light sensor. During the laser beam is transmitted through the optical system, the object lens movably supported by suspension wires are driven by a driving mechanism so as to be adjusted on an appropriate position in the focusing and the tracking directions. The driving mechanism has focusing and tracking coil. The focusing and the tracking coils are provided by the object lens supporting unit.
Often, the suspension wire has been already warped in a stage when the suspension wire is prepared in order to assembling the object lens supporting unit. This is because the suspension wire is like as a piano wire. If the object lens is supported by the warped suspension wire, an optical axis of the object lens is deviated in the tracking direction from a standard or a datum position. Furthermore, even if the object lens is supported by the warped suspension wire with the optical axis in the standard position, the suspension wire and the other parts of the object lens supporting unit adjacent to the wire are stressed. The object lens supporting unit in which the parts are stressed degrades in movement. Although it may deal with the matter mentioned above to assemble the object lens supporting unit with sorting out the warped suspension wire and only using the suspension wire not warped, it reduces manufacturing efficiency and increases manufacturing cost.